1. Field of the Invention
The present invention relates to a knotting method which is applicable to a netting production line, particularly a fishing net production line.
2. Description of Prior Art
Fishing nets are generally classified in terms of structure mainly into three types, i.e., a knotted net, a knotless net and a twisted net, and a predominant one of the three different types of nets is the knotted net. Further, knots of knotted nets are divided broadly into an English knot, a double English knot, and a reef knot or flat knot. Among the three kinds of knots, the English knot is superior to the others with respect to production efficiency and costs. The double English knot is an improved version of the English knot in terms of firmness of knot and allows a minimum of change in the mesh configuration to occur in a product. Traditionally, the double English knot has been believed to be the supreme knot configuration for a gill net which is made of nylon.
Meanwhile, since it has been reported that a gill net constituted by nylon monofilaments increases the haul, nylon monofilaments are increasingly used as a material of gill nets. However, because a nylon monofilament is highly stiff and slippery, the traditional knotting means as described above render a gill net which is constituted by intertwined nylon monofilaments liable to deformation of its meshes. To achieve firmer knots, various knotting methods have heretofore been developed which intertwine a warp yarn and a weft yarn in a complicated configuration to avoid deformation, or shifts, of the meshes. A problem with a gill net having such firm knots is that the productivity is limited because knotting relies on complicated intertwining of a warp yarn and a weft yarn as stated. Another problem is that, because only rigidity of knots is pursued, the knotted portions are conspicuously large and therefore, obstructive to the enhancement of haul.